It was shown here that orthodox etching in molten KOH-NaOH eutectic (E etch and its modification) and photo-etching in aqueous KOH solution permitted the rapid assessment of density, distribution and, after appropriate calibration, the type of defects in GaN single crystals and epitaxial layers. It was shown that dislocations and micro-defects could be revealed in the form of etch pits (in orthodox E etch) and as etch hillocks (photo-etching method) on both the Ga- and N-polar surfaces. The reliability of both methods was confirmed by direct transmission electron microscopic calibration and by using indentation methods. A very low dislocation density (etch-pit density of up to 2 x 102/cm2) in the undoped GaN single crystals and MOCVD-grown epitaxial layers was confirmed.

Characterization of GaN Single Crystals by Defect-Selective Etching. J.L.Weyher, L.Macht, G.Kamler, J.Borysiuk, I.Grzegory: Physica Status Solidi C, 2003, 0[3], 821-6